The present invention relates generally to multiple lip seals, and particularly to multiple lip oil and grease seals which may be made at reduced cost by reason of being able to be accommodated in a relatively large variety of sealing applications.
In the preferred form, the invention is directed to so-called bonded seals, as distinguished from assembled seals, that is, to seals wherein the lips are molded from natural or synthetic rubber at the same time the seal body is bonded to a casing unit, normally made from metal. The casing serves the dual purpose of providing radial stiffness and location for the seal lips as well as acting to provide a surface for mounting the seal. In this connection, seals of this type are most commonly secured in a counterbore in a machine housing, but they are also sometimes made in a so-called outwardly acting configuration, with the lips extending radially outwardly from the shaft and lying in contact with a flange or other movable part.
Multiple lip oil and grease seals are commonly used in severe service environments, particularly those wherein grease may be the sealed medium. An advantage of seals of this sort is their ability to function effectively even though one or more lips may become abraded by the presence of contamination exterior to the sealed region. Such multiple lip seals having the capability of running at relatively lower temperatures than a seal having a single, extremely wide lip forming a seal band or a path of shaft contact in the sealed application. However, in the past, in spite of the relatively simple, straightforward nature of multiple lip seals, there has been a problem of unduly high cost of manufacturing such seals. Although multiple lip seals are manufactured in large numbers, there is a large range of seal sizes, and consequently, most production runs of any one size seal are quite small. Consequently, tooling and other costs tend to be high in relation to the total number of seals made.
In the past, some seal designs have required that the rubber body of the seal be reinforced throughout a significant part of its axial length. Therefore, some seal designs have utilized a combination of stiffening member and mounting flange as a single unit. Most commonly, this has resulted in a seal construction wherein the annular rubber body from which the lips extended lay entirely inside an annular seal casing. The steel casing was then pressed into a counterbore, with the lips extending radially inwardly to seal an associated shaft.
In other cases, the metal stiffener was surrounded entirely by the seal body with a relatively thin band or annulus of rubber lying radially outside some or all of the stiffening flange. This created a so-called "rubber O.D." (outside diameter) seal, wherein the secondary or static seal was achieved by contact between rubber on the seal unit and metal in the counterbore or other seal assembly. The same design would be applicable to an outwardly acting seal, except that the stiffener would lie radially inwardly of the lips. In the prior art, where there were various O.D.'s for a given I.D. (inside diameter), or vice-versa, the cross-section of the seal body was increased accordingly. Where the difference was large, excess rubber was used. Where the differences were very large, a thick body was usually designed, and the axially extending metal flange was eliminated. This design was also wasteful of rubber; both types of prior art designs required separate tooling for each side. Accordingly, with a shaft of the given diameters being used in association with several different counterbores, several different size seals would be tooled and manufactured, creating an excessively large inventory of a relatively small number of interchangeable parts.
According to the present invention, a second, but inexpensively manufactured, mounting flange is provided in a multiple lip seal which includes an axially extending flange serving to reinforce the body. In this manner, a number of different size stampings or seal casings can be made, differing from each other only in radial size, but having a common inner diameter which serves as a stiffener and body mounting portion. Thereupon, in manufacturing the same tooling can be used to manufacture seals of different diameters, and accordingly, tooling costs may be substantially reduced with the result that lower cost seals may be manufactured.
Accordingly, it is an object of the present invention to provide an improved multiple lip oil seal.
Another object of the invention is to provide an oil seal which is capable of manufacture at decreased cost, and in particular, in which the body can be made from a single tool as opposed to the requirement of being made from a family of tools.
Another object is to provide a multiple lip seal which is easy and reliable to install in use.
Still another object of the invention is to provide a seal which, by its nature, is able to provide a readily accessible, highly effective flash barrier for cooperation with other mold parts used to form the seal.
Another object of the invention is to provide a seal which may be readily manufactured using tooling not requiring change parts for interchangeability, but wherein the interchangeability feature of the seal may be made by the use of parts entirely extrinsic to those used in tooling.
The present invention achieves these and other objects by providing a seal having a casing element comprising two spaced apart, axially extending flanges joined by a radial flange which serves as a flash barrier for a movable mold part, and which includes a seal body portion having a plurality of radially extending sealing lips, including axially inner and outer lips and at least one intermediate lip, with one axial flange of the casing having an extent sufficient to radially overlie at least parts of all of the seal lips.
The manner in which these and other objects and advantages of the invention are achieved in practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example and shown in the accompanying drawings, wherein like reference numbers indicate corresponding parts throughout.